Abstract: A minimum value (MV) is computed for start timestamps that each correspond to an uncommitted transaction. In an embodiment, the MV is computed for a pluggable database that is open on at least first and second instances of a database. The MV is computed for the first instance as of a first current timestamp (CT). The MV and the first CT are communicated to a second instance that has a second CT. If the first and second CTs are equal, the second instance store the MV. If the first CT is bigger, the second CT also becomes equal to the first CT. If the first CT is smaller, the MV is discarded, and the first CT becomes equal to the second CT. In an embodiment, if the MV remains unchanged for a predetermined time period, a start timestamp corresponding to the MV is advanced to a current or future timestamp.

Abstract: A minimum value (MV) is computed for start timestamps that each correspond to an uncommitted transaction. In an embodiment, the MV is computed for a pluggable database that is open on at least first and second instances of a database. The MV is computed for the first instance as of a first current timestamp (CT). The MV and the first CT are communicated to a second instance that has a second CT. If the first and second CTs are equal, the second instance store the MV. If the first CT is bigger, the second CT also becomes equal to the first CT. If the first CT is smaller, the MV is discarded, and the first CT becomes equal to the second CT. In an embodiment, if the MV remains unchanged for a predetermined time period, a start timestamp corresponding to the MV is advanced to a current or future timestamp.

Abstract: Techniques related to query execution against an in-memory standby database are disclosed. A first database includes PF data stored on persistent storage in a persistent format. The first database is accessible to a first database server that converts the PF data to a mirror format to produce MF data that is stored within volatile memory. The first database server receives, from a second database server, one or more change records indicating one or more transactions performed against a second database. The one or more change records are applied to the PF data, and a reference timestamp is advanced from a first to a second timestamp. The first database server invalidates any MF data that is changed by a subset of the one or more transactions that committed between the first and second timestamps.

Abstract: A method and apparatus for updating databases are disclosed. In response to a flashback request, a database object is restored to a state as of a specified flashback time. The changes introduced into the database object are reversed in a sequence starting with a change introduced into the database object immediately before issuance of the flashback request and ending with a change introduced into the database object immediately after the specified flashback time.

Abstract: A technique for making versions of rows of a user-defined tracked table temporally queryable. The database management system of the technique permits temporal queries of user-defined tables. The queries return versions of rows in the user-defined table that are currently in an undo log maintained by the database system. Associated with the tracked table are a system history table which contains versions of the rows and temporal metadata indicating when the versions were in the tracked table and a system form history table which contains versions of the form of the tracked table and metadata indicating when the tracked table had the form. These tables are created and maintained by a background process in the database management system. A temporal query on the tracked table combines results from the undo log with results from the system history table. The results' form is determined by the system form history table.

Abstract: Methods and systems for automatically tuning the undo retention in a database system are disclosed. The undo tablespace may be of a fixed size or may be set to be automatically extended. If the undo tablespace is of a fixed size, the undo retention is set to a “best possible” undo retention, which is calculated based on statistical data stored in the system. If the undo tablespace is configured to be automatically extensible, the undo retention may be set to be greater than the duration of the longest running query in the system. The duration of the longest running query may be calculated in a distributed process in which each instance broadcasts information about its longest running query to other instances.

Abstract: Methods and systems for using undo hints to speed up segment extension are disclosed. While a process is searching other segments to find available space, the process collects undo hints that describe when space in a segment might become available. These undo hints are placed in a table of undo hints. When a process is not able to find available space, it may consult the table of undo hints to determine how much to decrease the undo retention. After the undo retention is decreased, the process may again consult the table of undo hints to find a segment that likely contains available space now that the undo retention time has been reduced.

Abstract: Techniques for avoiding lock contention when processing data definition language (DDL) statements are provided. Some DDL statements modify metadata of a table and then require access to the table. After such a DDL statement modifies the metadata of a table and the updated metadata is made available (i.e., published) to other database statements, execution of the DDL statement is suspended. Data manipulation language (DML) statements acquire locks on the table. In one approach, the locks, of any DML statement, that are granted after the DDL statement is issued are timestamped. The DDL statement uses the timestamps to determine when to access the table. The timestamps are used to determine when the last DML statement (that was pending at the time the modified metadata was published) commits and releases its lock on the table.

Abstract: A method and apparatus for data recovery are disclosed. A plurality of queries executing in a database system are tracked. A query with a longest duration is selected and undo retention duration is calculated for supporting the longest query.

Abstract: A method and apparatus for updating databases are disclosed. In response to a flashback request, a database object is restored to a state as of a specified flashback time. The changes introduced into the database object are reversed in a sequence starting with a change introduced into the database object immediately before issuance of the flashback request and ending with a change introduced into the database object immediately after the specified flashback time.

Abstract: An intelligent database infrastructure wherein the management of all database components is performed by and within the database itself by integrating management of various components with a central management control. Each individual database component, as well as the central management control, is self-managing. A central management control module integrates and interacts with the various database components. The database is configured to automatically tune to varying workloads and configurations, correct or alert about bad conditions, and advise on ways to improve overall system performance.

Abstract: A method and apparatus for updating databases are disclosed. In response to a flashback request, a database object is restored to a state as of a specified flashback time. The changes introduced into the database object are reversed in a sequence starting with a change introduced into the database object immediately before issuance of the flashback request and ending with a change introduced into the database object immediately after the specified flashback time.

Abstract: Techniques for avoiding lock contention when processing data definition language (DDL) statements are provided. Some DDL statements modify metadata of a table and then require access to the table. After such a DDL statement modifies the metadata of a table and the updated metadata is made available (i.e., published) to other database statements, execution of the DDL statement is suspended. Data manipulation language (DML) statements acquire locks on the table. In one approach, the locks, of any DML statement, that are granted after the DDL statement is issued are timestamped. The DDL statement uses the timestamps to determine when to access the table. The timestamps are used to determine when the last DML statement (that was pending at the time the modified metadata was published) commits and releases its lock on the table.

Abstract: A technique for making versions of rows of a user-defined tracked table temporally queryable. The database management system of the technique permits temporal queries of user-defined tables. The queries return versions of rows in the user-defined table that are currently in an undo log maintained by the database system. Associated with the tracked table are a system history table which contains versions of the rows and temporal metadata indicating when the versions were in the tracked table and a system form history table which contains versions of the form of the tracked table and metadata indicating when the tracked table had the form. These tables are created and maintained by a background process in the database management system. A temporal query on the tracked table combines results from the undo log with results from the system history table. The results' form is determined by the system form history table.

Abstract: Methods and systems for using undo hints to speed up segment extension are disclosed. While a process is searching other segments to find available space, the process collects undo hints that describe when space in a segment might become available. These undo hints are placed in a table of undo hints. When a process is not able to find available space, it may consult the table of undo hints to determine how much to decrease the undo retention. After the undo retention is decreased, the process may again consult the table of undo hints to find a segment that likely contains available space now that the undo retention time has been reduced.

Abstract: Methods and systems for automatically tuning the undo retention in a database system are disclosed. The undo tablespace may be of a fixed size or may be set to be automatically extended. If the undo tablespace is of a fixed size, the undo retention is set to a “best possible” undo retention, which is calculated based on statistical data stored in the system. If the undo tablespace is configured to be automatically extensible, the undo retention may be set to be greater than the duration of the longest running query in the system. The duration of the longest running query may be calculated in a distributed process in which each instance broadcasts information about its longest running query to other instances.

Abstract: A method and apparatus for performing file system operation locks at a database server is provided. A request to perform a file operation on a portion of a file managed by a database server is received at the database server. In response to receiving the request, the database server grants a lock that covers only a portion of the file that is involved in the file operation. For example, the database server may grant a lock that covers a range of bytes on the file, where the range of bytes is less than the entire file. Thereafter, the database server performs the file operation on the file. The file operation may be a NFS operation.

Abstract: A method and apparatus for data recovery are disclosed. A plurality of queries executing in a database system are tracked. A query with a longest duration is selected and undo retention duration is calculated for supporting the longest query.

Abstract: A method and apparatus for updating databases are disclosed. In response to a flashback request, a database object is restored to a state as of a specified flashback time. The changes introduced into the database object are reversed in a sequence starting with a change introduced into the database object immediately before issuance of the flashback request and ending with a change introduced into the database object immediately after the specified flashback time.

Abstract: An intelligent database infrastructure wherein the management of all database components is performed by and within the database itself by integrating management of various components with a central management control. Each individual database component, as well as the central management control, is self-managing. A central management control module integrates and interacts with the various database components. The database is configured to automatically tune to varying workloads and configurations, correct or alert about bad conditions, and advise on ways to improve overall system performance.